Polymers of polyfluorothioketone



3,069,396 PULYMES F PLYFLURTHIOKETGNE Wiiliam ll. Middieton, Claymont, Del., assigner to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Feb. 9, 1959, Ser. No. 791,860 i7 Claims. (Cl 26d-79) This invention relates to, and has as its principal objects provision of, polymers of certain fluorinated organic compounds containing sulfur and the preparation of the same.

Fluorinated compounds of various types are known and many of them possess properties that make them valuable in particular applications. Although uorine is very active, fluorinated hydrocarbons are generally inert. High molecular weight liuorinated compounds have found utility where thermal stability is required. In general, sulfur compounds are not considered to possess a very high degree of chemical and thermal stability.

ln accordance with the abovementioned and yet other objects which will be evident from the remain-der of this specification, there are now produced novel polymers of polyfluorothioketones in which the carbons attached to the thiocarbonyl carbon are free from hydrogen. A preferred group of polymers are of the polyiiuorothioketo-nes which have the general formula are generally linear polymers, including copolymers of the polyfluorothioketones with other copolymerizable monomers.

These new high molecular weight linear polymers are obtained by subjecting the monomeric polyfiuorothioketone to a temperature of below about 80 C. generally in the presence of, as a catalyst, a compound providing or accepting a pair of electrons (i.e., a Lewis acid or base). The temperature employed is below that of solid carbon dioxide and generally is obtained by liquid air or similar coolants. The temperature is generally 80 C. to about 200 C. with 120 C. or below preferred.

When the temperature is above about 80 C., the monomeric polyfiuorothioketone can be converted to the corresponding dithietane, Le., the cyclic dimers The conversion is facilitated by the presence of a Lewis base and takes place most readily at temperatures of 75 to 100 C. When the temperature is maintained at 50 -to 80 C., most of the pure monomeric polyfluorothioketones are stable for considerable periods of time. At temperatures of above about 400 C., the dithietane is converted to monomer.

The exact temperature at which the monomer is converted to linear high polymer rather than to cyclic dimer depends upon the nature of the monomer and the catalyst. Below about 120 C. linear polymer is the major product whereas between 120 and 80 C. dimer may form along with the linear polymer.

111e conversions to linear polymers are brought about under essentially liquid phase conditions, i.e., liquid to semi-solid conditions. Solvents for the monomers that are liquid below 80 C. and preferably below 120 C., e.g., dimethyl ether, ethane, propane, butane, and the lCe like, are employed to dissolve the monomeric polyuorothioketone and catalyst added. The solution can be froz en by rapid cooling. Upon warming to the liquid state, polymerization takes place. The polymerization is readily followed by observa-tion of the fact that the blue-colored monomer is converted to colorless solid polymer which precipitates from any solvent present. Although solvents are generally preferred, linear polymers form in the absence of added solvents under the above conditions.

Separation of reaction products from each other and from unreacted materials according to the process of the invention can be readily accomplished by obvious methods. Thus dimer, linear polymer, unreacted monomer and diluent, where used, can easily be separated by fractional distillation taking advantage of the differences in boiling points. Other methods of separation are, however, available, as will be readily understood.

This invention is illustrated in further detail by the following examples wherein l-lV illustrate dithietune preparation, and V-XI show the preparation of linear 1 polymers.

EXAMPLE I Tetra/cis( T rifluoromethyl -1 i-Dithzetmze (Also Named PerfluOrotetramezy.(-1,3-Dithietmre) CFs S C Perfluoropropanethione, 0.7 g., was sealed in a glass tube and allowed to warm from C.. to room temperature. The color faded from deep blue to green and then to yellow over a period of five hours. The resulting liquid was frozen in an ice bath and sublirned at l mm. pressure into a trap cooled by solid carbon dioxide/acetone. There was obtained 0.25 g. of peruorotetrarnethyl- 1,3-dithietane as a white solid, M.P. 22-23 C.

Analysis-Calm. for CGFMSZ: C, 19.79%; F, 62.6l%; S, 17.61%. Found: C, 19.64%; F, 62.36%; S, 17.52%.

Peruorotetramethyl-l,3-dithietane is useful for conversion by pyrolysis to its monomer and, in the liquid state, as an inert transformer duid.

EXAMPLE H Mercury, 40.2 g., was added dropwise to a iiask containing g. of sulfur heated to reflux. A total of 108 g. of bis(heptauoro2propyl)mercury was then added dropwise over a period of two hours. A slow stream of nitrogen was also passed through the reaction mixture during the addition. The eiuent gases were condensed in a trap cooled by solid carbon dioxide/ acetone. At the end of the reaction the trap contained a mixture of a deep blue liquid and a white solid. The more volatile blue component was distilled at reduced pressure from the trap into another trap cooled by liquid nitrogen. The deep blue-black distillate (hexailuorothioacetone) was allowed to warm slowly to room temperature under autogenous pressure. After 16 hours the blue color had faded to yellow. Distillation of this material gave 19.6 g. of a light yellow oil, B.P. 99 lll C. Examination of the n-m-r spectrum of this material indicated that it was principally tetrakistriuoromethyl 1,3 dithietane with small amounts of impurity present.

The impure dimer was shaken with 50 ml. of 10% sodium hydroxide and 25 ml. of 30% hydrogen peroxide until the initial exothermic reaction had subsided. The organic layer was separated, dried over silica gel, and distilled. There Was obtained 13.8 g. of tetrakis(triiiuoro methyl)1,3dithietane as a colorless oil, B.P. 110 C., M.P. 22 23 C.; 111325, 1.3360. Identification was made `by analysis of its n-rn-r spectrum.

3 EXAMPLE n1 Dzmer of Hexafluarothoacetone T elm/cis( T rz' fiuoromethyl -1 i-Dithz'etane A solution of g. (0.038 mole) of triphenyl phosphine in ml. of acetone was added dropwise to 10.05 g. (0.025 mole) of bis (heptauoro-Z-propyl)disulfide cooled in ice. After one hour, the reaction mixture was distilled to dryness under vacuum, and the distillate was drowned in water. The organic layer was separated, dried over silica gel, and distilled. There was obtained 4.98 g. of tetrakis(triuoromethyl)-1,3dithietane as a colorless liquid, B.P. 110-111o C. The product was identilied by its n-m-r spectrum and comparison with other samples.

The dithietane was similarly prepared by reaction of a mixture of bis(heptauoro-Z-propyl)disulfide, trisulde, and tetrasuliide with triphenyl phosphine.

These sullides were obtained as follows: A 40G-ml. bomb containing 156 g. (0.29 mole) of bis(heptauoro 2propyl)mercury and 32 g. (1 mole) of sulfur was heated at 220 C. for 12 hours. The bomb was cooled and vented, the residue was filtered, and the ltrate distilled. There was obtained 30.5 g. of bis(heptafluoro2 propyl)disultide, B.P. 11G-124 C., 39.5 g. of bis(hepta uoro-Z-propyl)trisulde, B.P. 150-155" C., and 12.7 g. of bis (heptafluoro-Z-propyl)tetrasulde, B.P. ISO-186 C.

Analysis.-Calcd. for C6F14S2: C, 17.9%; S, 15.9%. Found: C, 17.9%; S, 15.3%.

Calcd. for C6P`14S3: C, 16.6%; S, 22.1%. Found: C, 17.0%; S, 22.0%.

Calcd. for C6C14S4: C, 15.4%; S, 27.4%. Found: C, 15.3%; S, 26.8%.

EXAMPLE V A yglass trap containing 1 ml. of BFa-etherate was immersed in liquid nitrogen and evacuated. Peruoropropanethione, 5 ml., was distilled into the trap. The trap was removed from the liquid nitrogen bath, and the frozen contents were allowed to melt slowly. Acetone, 15 ml., was added to the trap when the blue color of the peruoropro-panethione had disappeared. The solid material in the trap was collected on a filter, washed with acetone, and dried. There was obtained 1.7 g. of polyperlluoropropanethione as a white, rubbery polymer, insoluble in most common solvents. The polymer was pressed at 50 C. and 10,000 lb./sq. in. into an elastomeric film.

Analysis-Calcd. for (C3F6S): S, 17.61%. Found: S, 17.28%.

EXAMPLE VI A solution of two drops of dimethylformamide in 5 ml. of ether contained in a glass trap was frozen in a liquid nitrogen bath. The trap was evacuated, and 2 m1. of perfluoropropanethione was distilled into the trap on top of the frozen ether. The entire frozen contents of the trap were warmed until about one half melted. The contents were frozen again by immersing the trap in the liquid nitrogen bath and then remelted several times until the blue color of the thioketone was discharged. The trap was allowed to warm to room temperature, and 25 ml. of acetone was added. The polymer was collected on a lter, washed `with acetone, and dried. There was obtained 0.7 g. of polyperiluoropropanethione as a white, rubbery solid.

Analysis-Calcd. 62.61%; S, 17.611 17.95

for (C3F6S): C, 19.79%; F, Found: C, 20.27%; F, 62.94%; S,

EXAMPLE VII A solution of one `drop of dimethylformamide in 5 ml. of pentane contained in a glass trap was frozen solid in liquid nitrogen. The trap was evacuated, and 1 ml. of pertluoropropanethione was distilled into the trap. The trap and its contents were allowed to warm slowly to room temperature. As soon `as the contents of the trap began to melt, they were mixed by vigorous shaking. After the trap had warmed to room temperature, l5 ml. of acetone was added and the white, rubbery polymer was collected. There was obtained 0.37 g. of polyperuoropropanethione.

EXAMPLE VIII The procedure described in Example Vil was repeated, except that two drops of ethyl alcohol were used in place of the dimethylformamide. There was obtained 0.35 g. of white, rubbery polymer.

EXAMPLE IX The procedure described in Example VII was repeated, except that two drops of benzenetihiol were used as the catalyst. There was obtained 0.19 g. of yellow, rubbery polymer.

EXAMPLE X The procedure described in Example VII was repeated, except that 1 ml. of `dry ethyl ether was used as the catalyst. There was obtained 0.37 g. of white, rubbery polymer.

EXAMPLE XI carbonyl group together are attached to at least two and generally at least four iluorines. The remaining substituents are halogen, hydrocarbon, or halohydrocarbon. preferred are compounds of the formula Rondo Fin wherein R groups are halogen, hydrocarbon, or halohydrocarbon, of up to six carbons. In addition -to the compounds 4and polymers `specifically disclosed in the preceding examples, by one or more of the methods previously described the following monomers are likewise available for conversion fto polymers: peruorohexane-Z- thione; peruorohept-ane 2 thione; periluorooctanethione; peruorononane-Z-thione; and 1,1,1,3,3penta uor-obutane-2-thione.

A further compound useful for polymer form-ation in this invention is triliuorothiacetophenone.

Mixtures of `different polyuorothioketones are also converted to dithietanes and to linear high copolymers. Likewise, copolymerization with other polymerizable monomers, such as thiocarbonyl fluoride (F2C=S), uoroalde'hydes, eg., trifluoroacetaldehyde, and thioacyl fluorides, eg., triuorothioacetyl fluoride, can be effected.

Although the conversion of monomeric pro-lyfluorothioketones `to dimer and linear polymer i.e., compositions having the recurring unit [merope-SA takes place without added catalyst, Lewis acids or bases generally expedite the polymerization. Particularly useful are dimethylfor-mamide and hydrocarbon ethers. The amount of initiator used lis subject to wide variation; thus it can vary from 0% (i.e., no added catalyst) to several hundred per cent (i.e., when the solvent such as ether acts as catalyst), based on the monomer weight. Generally up to 25% is preferred.

The linear polymers of polyuorothioketones according to this invention possess Aat least ten recurring monomeric groups and a molecular weight of at least about 2000. They are generally elastomeric and exhibit considerable inertness to attack by corrosive chemical reagents. The polymers can be extruded under pressure and at elevated temperature (e.g., above 50 C.) and at pressures of 10,000 lb./sq. in. or more to provide shaped objects. They can be extruded on wires to provide ilexible insulation, Self-supporting lms obtained from the polymers are useful as gasket material. Filaments are likewise obtained from the polymer by extrusion and are useful in the preparation of elastic fabric resistant to solvent attack.

Although the linear polymer itself is not stableat high temperatures, treatment with reagents such as phosphorus pentachloride increases the heat stability. Similar improvement is obtained by lcontacting the polymer with olefmic compounds, e.g., cyclopentene, at room temperature for a few hours prior to shaping.

Since obvious modifications in the invention will be evident to those skilled in the `chemical arts, l propose to be bound solely by the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined `as follows:

1. A linear hompolymer having at least about recurring monomeric groups of a polyuorothioketone of the formula s RCFZiiCFZR' wherein R and R are selected from the group consisting of lluorine, chlorine, lower alkyl and polyfluoro-lower alkyl.

2. A linear homopolyemer of peruoropropanethione having at least about 10 recurring monomeric groups.

3. A linear copolymer of (1) a polyuorothioketone of the formula Rorgorm.' wherein R and R' are selected from the group consisting of uorine, chlorine, lower 1alkyl and polyuoro-lower alkyl `and (2) another polymerizable monomer selected from the `group consisting of polyuorothioketones of the `formula above, polylluoro-lower alkyl aldehydes and polyuoro-lower alkyl -tbioacyl uorides.

4. A linear copolymer of peruoropropanethione and another polymerizable monomer selected from the group consisting of polyuorothioketones of the formula above, thiocarbonyl fluoride, polyuoro-lower alkyl aldehydes and polyuoro-lower alkyl thioacyl liuc-rides.

5. A shaped object formed `from a solid polymer of claim l.

6. A shaped object formed from the linear homopolymer of claim 2.

7. A iilm formed from the linear hompolymer of claim 2.

8. A lament `formed from the linear hompolymer of claim 2.

9. A shaped object formed from a sol-id polymer of claim 3.

l0. A shaped object formed from a solid polymer of claim 4.

1l. The polymerization process which comprises subjecting at least one polyuorothioketone of the iformula wherein R and R are selected from the group consisting of lluorine, chlorine, lower talkyl `and polyfluoro-lower alkyl, `in the liquid phase to a temperature between about 100 and 200 C.

12. The polymerization pro-cess of claim l1 accomplished in the presence of a catalyst selected from the group consisting of boron triiiuoride-ethereate, dimethylformamide, liquid saturated hydrocarbon others, lower alkanols land benzenethiol.

13. The polymerization process which comprises subjecting perfluoropropanethione to a temperature of between tabout 100 and 200 C.

14. The polymerization process of claim 13 wherein the temperature is between about 0 and --80u C.

15. The polymerization process of claim 13 wherein the temperature is between about and 200 C.

16. The polymerization process of claim 13 accomplished in the presence of a catalyst selected from the group consisting of boron trilluoride-ethereate, dimethylformamide, liquid saturated hydrocarbon ethers, lower alkanols and benzenethiol.

17. rIlhe polymerization process of claim 13 wherein the perlluoropropanethione contains a second polymerizable monomer selected from the group consisting of polyfluoro-lower alkyl aldehydes and polyuoro-lower alkyl -thioacyl lluorides.

References Cited in the rile of this patent Journal of the Chemical Society, London, 1955, pages 3871-80 (page 3876 relied on).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIGN Patent Noo 3,06%396 December 18, 1962 William J. Middleton 1t s hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5(I line 33,I for "hompolymer" read homopolymer line 42, for "'homopolyemer" read ehomopolymer column 6, lines lO and 12q for "hompolymermw each oeeurrencev read homopolymer Signed and sealed this 10th day of September 1963.,

(SEAL) Attest:

ERNEST w.. SWIDER DAVID L- LADD ttesting @fficer Commissioner of Patents 

1. A LINEAR HOMPOLYMER HAVING AT LEAST ABOUT 10 RECURRING MONOMERIC GROUPS OF A POLYFLUOROTHIOKETONE OF THE FORMULA 